The utilization of single-walled carbon nanotubes (SWNTs) in large quantities in the fields of molecular electronics, opto-electronics, and biological sensing will require SWNTs of the same physical structure, electronic type, and band gap. Since current methods of synthesis produce mixtures of nanotubes with different physical structures and electrical properties, the development of methods for the post-production separation of these one-dimensional materials is necessary. Towards this end, progress has been reported in the separation of semiconducting from metallic SWNTs using controlled electrical breakdown, dielectrophoresis, and chemical moieties that selectively react with either type of nanotube.
SWNTs have been used in conjunction with various separation techniques, including anion exchange media, the protonation and ozonation of nanotube-sidewalls, and the light-induced oxidation of carbon nanotubes. However, such procedures chemically or structurally modify the nanotubes, at risk of compromising their properties and utility. Accordingly, the search for an efficient, economical separation method remains an ongoing concern in the art.